Telephone-transmitter



Patented Mar. 23,1920.

IIIIIIIIIIII ARTHUR ROBERT KAEL, 0F WITHINGTON, ENGLAND.

TELEPHQNE-TRANSMITTER.

Specification of Letters Patent. Patentd B131. 23, 1920.

Application filed March 20, 1916. Serial No. 85,246.

To all whom it 'may concern: v

Be it known that I, ARTHUR R. KAHL, a citizen of the United States, residing at 59 Burton road, VithingtOn, Manchester, England, have invented certain new and useful Improvements in Telephone-Transmitters, of which the following is a specification.

My invention relates to an' improved form of telephone .transmitter in which l pr'ovide an improved mounting means for the var iable resistance element so that the delicate diaphragm of said element is relieved from undue strains in the assembling and adjusting operation. l My invent-ion consists essentially in providing` the variable resistance element with a projecting stud or arm by which the element is rigidly supported from the framework or bridge of the transmitter, this. being accomplished by mounting on the bridge a bushing rigidly secured to but insulated from the bridge, which loosely receives said stud, and when the parts of the transmitter have been assembled, securing the stud and bushing together by means of material between them, such as solder, cement, etc., so that the stud and bushing are united and in effect become a rigidK structure held without clamping action upon said stud. ln the past it has been common to secure the variable resistanceielement to the bridge by means of a clamping screw, and this has been found to place considerable distortion in the delicate diaphragm of the variable resistance element so that its free operation was subsequently interfered with.

My invention will be better understood by reference to thedrawings, which are as follows: i

Figure 1 is alongitudinal sectional view through a completely assembled transmitter, some of the parts being shown in elevation for clearness;

Fig. 2 shows in longitudinal central sectional view the variable resistance element, together with its mounting means; and

Fig. 3 is a back view to a reduced scale of the complete transmitter with the outer protecting back shell removed.

Similar numerals refer to similar parts throughout the several views.

As shown in Fig. l, the transmitter consists of a front plate 10 in which the usual mouthpiece 11 is mounted, and upon the inner surface of which the edge ef the main diaphragm 12 rests. A thin ring of insulating material 13, suoli, for example, as mica or empire cloth, is disposed between the diaphragm and the front plate l0 to somewhat deaden the metallicA vibrations that might otherwise be readily set up in the diaphragm. The front plate l0 has secured to its rear surface a bridge 14, bent rearwardly at its middle portion, to mount the rear end of the variable resistance element 15, the front end of which is secured by clamp nuts, as indicated, to the central portion of the main diaphragm 12.

As seen more clearly in Fig. 2, the bridge 111 has mounted at its middle portion a first bushing` 16 insulated from said bridge as shown', and held in place by a nut 17 The bushing 16 is provided with a bore sufficiently large to receive `within it a second bushing 1S, which may be moved longitudinally in said bore to adjust it to the proper position, and when in said position it is securely held in place in the bushin 16 by means of the set screw 19 extending t irough the enlarged end or head of the bushing 1G. The variable resistance element 15` is of a construction similar to that found in telephone transmitters, and consists of a cup portion for receiving the back electrode 20, which is held in place by a clamping ring 21 screwed into the cup portion. The front of the element is closed by a thin mica diaphragm 22 held in place by an inwardly flanged ring 23 screwed on the outer end of the threaded ring 21. The mica diaphragm 22 is clamped between the disk 24 carried `by the screw stud25, and a disk 26 held in place by a nut 27 Both disks are preferably of metal and the inner disk has secured to it the front electrode 28. A second nut 29 on the screw stud 25 clamps the main diaphragm 12 against the nut 27, a connector 30 being interposed between the diaphragm and the nut 27. The central portion of the rear wall of the cup is provided with a boss,` into which is screwed the threaded end of a stud or arm 3l, which stud is preferably of somewhat smaller diameter than the bore of the bushing 1S. A second connector 32 is clamped under the nut 17 so that electrical connection may readily be made with the back electrode.

ln assembling the transmitter the resistance element 15 is secured to the main diaphragm by means of the nuts referred to withthe connector 30 in place and placed in proper position against the front plate 10,

the insulating ring 18 being interposed as described. The bridge 11i with the stud 16 and connector 32 rigidly secured thereto are then put in position against the projecting lugs a of the front plate and screwed thereto as indicated. The resistance element and main diaphragm are then adjusted until the stud 3l is centered in the bushing 16, and the sleeve 18 is put in place so that its o-uter end is somewhat forward of the rear end of the stud 31, in which position the bushing 18 is securely clamped by the screw 19. rIhe bushing 18 and the outer end of the stud 81 are preferably tinned before being assembled. The dampening springs 33 are then screwed in place, their inner ends resting against a disk 311 of insulating material, such as empire cloth, which was placed back of the main diaphragm in its assembly with the resistance element. The outer end of the connector is then screwed to the binding'post 35 carried by and insulated from the bridge, the other connector 32 having previously been secured to the other binding post 36 similarly mounted upon the bridge. Vith the dampening springs properly adjusted so that the stud 31 is free in the bushing 18 and so that the proper tension is eX- erted upon the main diaphragm 12, the' bushing 18 and the stud 31 are secured together by running melted solder around Or between the ends of the bushing and the stud so as to unite these parts together to form a rigid structure, without,however, exerting any strain or cramping effect upon the stud, as would be the case if a clamping screw were used'against said stud. The inclosing shell or casing 37 is then putin place and secured to the front plate 10 by suitable screws in a manner well known in the art to inclose and protect the parts of the transmitter. While I find it convenient to employ solder for securing the stud 3l and bushing 1S together, it will be unde-rstood that other materials may be employed for this purpose, such, for example as brazing spelter of any kind or any suitable cement which has suiicient fluidity either as the result of heating' or'the presence of a proper solvent to flow into the space between the bushing and the stud. Furthermore, the stud and bushing may be secured or united together to form a rigid structure in other ways, as for example, by electric welding, in which case the filling material may fully or in part be furnished by the stud or bushing or both. y

As a result of the improved construction described, it will be observed that the resist-. ance element is rigidly secured to the bridge ofy the transmitter without bringing any strain of any kind to bear upon the resistance element, and that therefore the delicate diaphragm of the resistance element is free to respond properly to the `slightest vibraelement. I do not limit myself, therefore, in

the claims to any particular transmitter construction7 but desire to claim broadly any transmitter construction in which the mounting Vof the variable resistance element is effected without subjecting the resistance elcment to cramping or binding, while at the same time affording a rigid and positive support for said stud.

The carbon granules commonly employed in telephone transmitters are not shown in the drawings, as their use in variable resistance elements is well known in the art and they require no special illustration or dcscription.

`What I claim is:

1. In a telephone transmitter, the combination of a mounting plate, a diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projecting from itsother side, a bushing carried by and insulated from said bridge for receiving said stud, and means for securing said stud and bushing together without displacement of said stud in said bushing.

2. In a telephone transmitter, the combination of a mounting plate, a diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projecting from its other side, a first bushing rigidly secured to said bridge and insulated therefrom and provided with a clamping screw, and a second bushing mounted in said first bushing and held therein by said screw and having a bore for receiving said stud, said second bushing and said stud being secured together by material around said stud and within said second bushing uniting them into a rigid structure.

3. In a telephone transmitter, the combination of a mounting plate, a diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projecting from its other side, and a bushing carried by and insulated from said bridge for receiving said stud, said bushing and said stud being attached to each other to form a rigid structure without displacement of said stud in said bushing.

4. In a `telephone transmitter, the combination of a mounting plate, a diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projecting from its other side, a bushing carried by and insulated from said bridge for receiving said stud, and material between said stud and said bushing attaching them together.

5. In a telephone transmitter, the combination of a mounting plate, diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projectingl 'from its other side, a bushing carried by and insulated from said bridge for receiving said stud, and material such as solder or cement between said bushing` and said stud connecting them to form a rigid structure.

6. In a telephone transmitter, the combination of a mounting plate, a diaphragm, a bridge secured to said plate, a variable resistance element secured on one side to said diaphragm and having a stud projecting from its other side, a iirst bushing rigidly secured to said bridge and insulated therefrom and provided with a clamping screw, a second bushing mounted in said iirst bushing and held therein by said screw and having a bore for receiving said stud, and material such as solder or cement between said bushing and said stud connecting them to form a rigid structure.

7. In a mounting for the variable resistance element of .a telephone transmitter, the combination of a stud projecting from a va riable resistance element, a rigidly supported bushing, and material between said stud and said bushing attaching them together.

8. In a mounting for the variable resistance element of a telephone transmitter, the combination of a stud projecting from a variable resistance element, and a rigidly supported bushing, said bushing and said stud being attached to each other to form a rigid structure without displacement of said stud in said bushing. j

9. In a mounting for the variable resistance element of a telephone transmitter, the combination oi a stud proj ecting` from a variable resistance element, a bridge, a irst bushing rigidly secured to and insulated from said bridge and having a set screw eX- tending through it, and a second bushing carried within said first bushing and held in place around said stud by said set screw, said second bushing and said stud being united to form a rigid structure.

10. In a mounting for the variable resistance element or a telephone transmitter, the combination of a stud projecting from a variable resistance element, a bridge, a` first bushing rigidly secured to and insulated from said bridge and having a set screw eX- tending through it, a second bushing carried within said first bushing and held in place around said stud by said set screw, and material such as solder or cement between said second bushing and said stud, connecting them to form a rigid structure.

l1. In a telephone transmitter, the combination of a front plate, two supporting members comprising a main diaphragm and a bridge supported by said front plate, a variable resistance element between said supporting members and having oppositely extending studs for connection to said members, a clamping device for securing one of said studs to its supporting member, the other stud entering a free clearance opening therefor in the other supporting member, and a solder connection between the last mentioned stud and its supporting member.

In witness whereof I hereunto subscribe my name this 22nd day of February, A. D.,

ARTHUR ROBERT KAI-IL. 

